1. Field of the Invention
The present invention relates to prosthetic joints and, more particularly, to a trial neck for a prosthetic joint such as for hip joint replacement.
2. Background Information
Prosthetic joint implants are currently surging in use and technology. In performing most prosthetic joint implants, what is known as a trial or provisional is used before a final prosthesis is used. The trial or provisional is used to select the proper joint prosthesis and/or to orient or align one or more of the components of the final joint prosthesis. The trial or trial components are temporarily implanted to achieve proper sizing, placement and/or orientation of the final joint prosthesis, as well as achieve anatomical orientation of the prosthesis and/or components of the joint prosthesis.
Hip arthroplasty provisionals or trials have a neck that is used to attach a femoral head provisional or trial thereto. The orientation of the neck relative to the shaft of the broach or trial is described in terms of anteversion, neck length, neck angle, and/or neck offset. Because each patient's original femoral neck anatomy is different, the ability to replicate the original femoral neck anatomy of each patient during hip arthroplasty requires multiple neck trials having variations orientations. The use of multiple neck segments is not advantageous since it requires more time, increased instrument cost and increased space in the instrument sterilization case
Thus, trialing systems utilized by many hip implants or prostheses generally consist of a broach and a neck segment. In order to intraoperatively change the offset of the trial (i.e. neck segment and broach), the neck trial must be removed and another neck trial must be put in its place. Thus, multiple neck trials that are exchangeable with one another relative to the broach are necessary in order replicate the original hip anatomy.
Other hip systems utilize only one neck segment with the offset incorporated into the location of the trunion of the broach. This design, however, does not mimic the exact geometry of the actual implant. While it is desired to be able to try several neck offsets relative to the broach in order to achieve a proper head positioning for the final implant, the prior art is deficient.
In U.S. Pat. No. 5,645,607 issued to Hickey, a hip trial or prosthesis having an adjustable neck portion is disclosed in which the problem of multiple neck trials is addressed. The adjustable neck of Hickey allows the trialing of various neck offsets in order to achieve a correspondence between the spatial orientation of a patient's original anatomy and a final implanted hip ball prosthesis.
However, Hickey requires a vertical height change of the neck segment in order to move between the various offsets. Where vertical height is restricted during surgery, especially in current, less invasive arthroplasty procedures, vertical height adjustment is undesireable.
It should be appreciated in view of the above, that it is desired to have a single trial neck for a trial prosthesis that provides a plurality of offsets.
It should be appreciated in view of the above, that it is further desired to have a single trial neck for a trial prosthesis that is usable in minimally invasive implant procedures.
It should also be appreciated in view of the above, that it is still further desired to have a single trial neck for a trial prosthesis that requires only one direction of movement to affect translation of the trial neck into a plurality of offsets.